The present invention relates to a laser based toe-in alignment apparatus for a vehicle having suspended, steerable wheels.
The toe of the front wheels of a vehicle is defined as the angular relationship of the principal plane of the front wheel to the vertical plane passing through the longitudinal axis of the vehicle. As viewed from overhead, toe dictates whether or not the tires roll straight down the road. We can refer to toe as the angle of attack for the tires as the vehicle is driven forward. If the front of the tires points towards the centerline of the vehicle, with both tires aiming inboard, this is called toe-in, because the tires on that axle are aiming inboard. If the front of the tires is aiming in an outboard direction, away from the centerline of the vehicle, this is referred to as toe-out. A slight amount of toe-in is normally desirable for good handling and tire wear characteristics.
The toe-in of the steerable front wheels of a vehicle has to be properly set since, if otherwise, poor steering and/or high rates of tire wear will occur. Generally, commercially available tools use a vehicle""s installed wheels to assess or establish wheel toe-in condition, and lasers and/or mechanical indicating devices are typically employed in these tools and processes. There are laser and mechanical devices and methods that use equipment attached across the vehicles steering components to indicate the state of toe-in. The use of a cross-vehicle mechanical apparatus requires time and care to establish and attachment or alignment to both wheels or rims to allow for toe-in setting and are not easily adapted to the environment of a manufacturing assembly line. One known alignment system required two operators to lift, locate and secure the device across the front of the vehicle. Indicating arms were located on each axle spindle and the tie rod ends were adjusted to bring each of the indicating arms into alignment with target lines on the cross-vehicle device.
U.S. Pat. No. 3,782,831 discloses a toe-in setting assembly including a pair of light-emitting and receiving devices respectively coupled to opposite steerable wheels, the devices being electrically coupled to a control console including display meters for indicating the toe-in angle in accordance with signals sent by the devices. This device requires significant care in its leveling and alignment with each wheel rim before measurements or adjustments can be accurately effected. The set up time for these types of devices are relatively long and significant time is required for an operator to master the technique of properly using these devices. U.S. Pat. No. 4,115,926 discloses a toe-in setting system which is said to overcome the need to level separate devices coupled to wheels, the separate devices of the patent each producing a beam of light and each including a lined target screen for receiving the light beam of the other device.
The prior art also includes a cross-vehicle mechanical apparatus that fastens to each king bolt and uses devices attached to each axle spindle to indicate toe-in relative to a target line of the apparatus. This equipment is time consuming to attach and has excessive setting variability due to parallax between the indicating elements, operator uncertainty with respect to target acquisition and also through the number of interfaces in the process. The weight of this cross-vehicle device needs to be minimized to allow for repeated lifting by assembly operators. The light weight requirement, however, creates a device that is not robust enough to maintain its shape through repeated use.
According to the present invention, there is provided an improved toe-in setting arrangement which includes a pair of companion toe gauges mounted to the opposite steerable wheels or wheel-mounting spindles of the vehicle.
An object of the invention is to provide a toe-in setting arrangement which includes a pair of companion toe gauges that are each of a simple, reliable design, with the procedure for setting the toe-in with the devices being one that can be quickly mastered by an assembly line worker.
A more specific object of the invention is to provide a toe-in setting arrangement as set forth in the immediately preceding object wherein the toe gauges are particularly adapted for being used in a vehicle assembly line prior to the wheels being mounted on the spindles.
Yet another object of the invention is to provide a toe-in setting arrangement, as defined in the foregoing objects, wherein the mounting of each companion toe gauge to the vehicle requires a minimum number of interfaces with the vehicle.
The objects of the invention are achieved by a toe-in setting arrangement including two opposite hand companion toe gauges, with each device being located on an opposite axle spindle and having a target and a laser light assembly aligned with the longitudinal axis of its associated king pin. Each target has a target face that is located along the axis of the associated king pin. The laser in the device produces a reference beam which is calibrated to produce the required toe-in angle. As the tie rod end is adjusted, the device""s laser beam locates the target face of the companion toe-in device. Since the target face is along the king pin axis and the axle spindle rotates about the king pin, each device can be rotated independently without displacing the target provided to the companion toe-in setting device. Thus, the king pins jointly serve as the datum for the toe-in angle.
These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings.